. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. representing a vertical section of a fecundated ovum at the moment ofexclusion,and before any organ has been de- • veloped. The vitellus or yolk («) forms the greatest part of the contained liquid mat- ter, and the egg is almost entirely filled by it: its colour is gene- rally that of yellow ochre, and sometimes has a saffron tinge. In some species the yolk is grey, white, or reddish brown; and in each case the colour of this part determines the ge- neral tint of the egg. If the yolk be consi- derably magnified, it is se
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. representing a vertical section of a fecundated ovum at the moment ofexclusion,and before any organ has been de- • veloped. The vitellus or yolk («) forms the greatest part of the contained liquid mat- ter, and the egg is almost entirely filled by it: its colour is gene- rally that of yellow ochre, and sometimes has a saffron tinge. In some species the yolk is grey, white, or reddish brown; and in each case the colour of this part determines the ge- neral tint of the egg. If the yolk be consi- derably magnified, it is seen to be composed of an infinite number of minute globules of various sizes, swimming in the albumen, or surrounded by it, and resembling so many small yolks. The albumen (6) is a transparent crystalline liquid, without distinct organical parts, and consequently not presenting any globules, sur- rounding the vitellus as far as the cicatricula, and intermediate in bulk or quantity to these. If an ovum be opened, and the liquid which it contains be poured out upon glass, the albu- men is seen to surround the globules of the vitellus and cicatricula exactly as the serum of the blood envelopes the crassamentum. In the interior of the egg the albumen is situated, like the cicatricula, externally to the yolk, and fills the interspace between the yolk and the exterior membrane of the egg. It is in this interspace that the first lineaments of the embryo appear, and here the head, thorax, members, integuments, and their appendages, and all the internal organs, without excepting the intestines, are successively developed. The cicatricula or germ (c) is the smallest and most important part of the ovum. It is situated immediately beneath the exterior co- vering, and at the centre of the circumference of the egg. It is distinguished by the naked eye in the form of a little white point. If it be examined with more care, we perceive that it is of a lenticular figure, and -is composed of a
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